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Tuesday, June 18, 2013
If the high thyroid levels in the blood stream are caused by subacute or painless thyroiditis, then the disease will go away by itself and it does not need treatment. While waiting for the disease to get better, the patient may take a drug called a "beta blocker". This drug can block some (but not all) of the effects of the thyroid hormone on the body, and can make the patient feel better until the disease goes away by itself.
The most common causes of an overactive thyroid are:
All of these conditions respond to the same three treatments
When surgery is used, the thyroid gland (or the part of the thyroid gland containing the tumor in cases of toxic adenoma) is surgically removed. Usually enough of the thyroid is removed so that thyroid levels drop low after surgery. This is not a problem, however, because we know how to make thyroid hormone in a pill. The pill is cheap, only has to be taken once a day, and has no side effects (as long as the correct dose is being used).
Rarely the surgery may be complicated by damage to the nerve to the voice box, which can result in temporary or permanent hoarseness in the voice. The likelihood of this complication varies with the experience and expertise of the surgeon. In specialized centers with very experienced surgeons the probability of complications is about 2%. Also in less than 1% of cases, there is damage to other glands near the thyroid called "parathyroid glands". The parathyroid glands keep the calcium level in the blood normal, and patients with damage to these glands from thyroid surgery will need to take calcium and vitamin D pills to keep the calcium levels in the blood normal - either temporarily or permanently. Another possible side effect is hypothyroidism, which can be treated with thyroid hormone pills.
Doctors have been using radioactive iodine to treat overactive thyroid glands since the mid 1940's. The nice thing about iodine is that it only goes to two places in the body. It either goes to the thyroid gland or it goes out in the urine. (A small amount is taken up by the salivary glands and intestinal cells). When the thyroid cells take up radioactive iodine, the nucleus of each cell is radiated. Breaks occur in the DNA. Later on, when the cells try to reproduce, the broken strands of DNA cause the daughter cells to die. It takes about three months for a dose of radioactive iodine to have its full effect on the thyroid gland.
Sometimes (especially when a toxic adenoma is being treated) radioactive iodine returns the patient to normal - thyroid hormone levels in the blood are within normal limits. Usually, however, radioactive iodine causes thyroid levels to become low and the patient must take thyroid pills for life. Radioactive iodine, in the doses used to treat an overactive thyroid, usually has no other side effects besides causing hypothyroidism.
Some patients with Graves' disease can develop an autoimmune attack on the tissues behind the eyes, which causes a pressure build up behind the eyes. This can result in bulging forward of one or both eyes, or it can cause the eyes not to work together correctly (which gives the patient double vision).
Eye problems can occur in Graves' disease before the thyroid overactivity, at the same time as the thyroid overactivity, or years after the overactive thyroid has been treated. Patients can get Graves' eye disease after treatment with surgery, radioactive iodine, or anti-thyroid drugs. It has been suggested in the medical literature that Graves' eye disease might be a little more common in patients who have been treated with radioactive iodine than in patients who have been treated with surgery or anti-thyroid drugs.
A third treatment for the overactive thyroid involves the use of anti-thyroid drugs. The two anti-thyroid drugs available in this country are propylthiouracil (usually referred to "PTU") and methimazole (also known as "Tapazole"). These drugs slow down the thyroid gland's production of thyroid hormone. The more drug you take, the slower the thyroid works.
Treatment is usually started with a large dose of the drug, which brings the thyroid levels down to normal. The patient then goes through a period of adjustment where blood tests are ordered every two to four weeks and the dose of the medication is changed until we find a dose that keeps the thyroid levels normal. After that, the blood tests may come less and less often until finally they are only checked every six months. These anti-thyroid drugs have been in use for several decades and the risk of severe side effects is small.
A few patients out of every 10,000 have been reported to develop liver trouble. Another rare side effect is called "agranulocytosis". This is a condition in which the white blood cells, which fight infection, disappear from the body. This could be a serious problem if an infection developed while those white blood cells were low.
Fortunately, there is usually a warning when you get agranulocytosis - a fever and a sore throat. Patients on anti-thyroid drugs who develop a fever and a sore throat should stop the pills and call right away to get a blood test. If the blood test shows agranulocytosis, patients must remain off the anti-thyroid drugs. The white blood cells usually return to normal within one to two weeks.
PTU, but not methimazole, has rarely been associated with severe liver disease. The FDA has recommended that PTU be used only in pregnant women during the first trimester and in patients who are allergic to or cannot tolerate methimazole.
Thus, each of the possible treatments for an overactive thyroid have some advantages and some disadvantage. In general, all three treatments are highly effective and associated with a low risk of side effects.
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Last Reviewed: Mar 25, 2013
Thomas A Murphy, MD, FACP, FACE
Associate Professor of Medicine
School of Medicine
Case Western Reserve University